羥乙基澱粉
**羥乙基澱粉 (HES)** 是一種源自蠟質澱粉（主要由支鏈澱粉組成）的合成膠體體積擴充劑。在獸醫重症監護中，它被用於治療低血容積並提供膠體滲透壓支持。 **主要臨床特徵：** * **血管內持久性：** 與晶體輸液相比，HES 能提供更好且更持久的血管內體積擴充效果。 * **微血管滲漏症候群：** 在全身性發炎的病患中，它有助於降低血管通透性並下調促發炎介質。 * **分子量與取代度：** 產品根據其平均分子量 (MW) 和取代度 (DS) 進行分類（例如 HES 450/0.7、HES 130/0.4）。較高的 MW 和 DS 通常會延長血管內半衰期，但會增加凝血異常的風險。
作用機制: HES acts as a synthetic colloid to expand plasma volume through oncotic forces. * **Oncotic Pull:** Large HES molecules remain in the intravascular space → **increase plasma oncotic pressure** → draw fluid from the interstitial space into the blood vessels → **expand circulating blood volume**. * **Enzymatic Degradation:** To prevent rapid breakdown, the glucose units of amylopectin are substituted with hydroxyethyl ether groups. * **Metabolism:** Larger molecules are slowly degraded by **serum alpha-amylase** into smaller fragments → fragments < 50,000 Daltons are rapidly excreted by the kidneys.
各物種劑量
- Shock bolus (resuscitation) · 5-10 mL/kg · IV · once · Administer slower than in dogs to avoid nausea/vomiting.
- Infusion · 1-2 mL/kg/hr; not to exceed 10 mL/kg in a 24 hour period · IV · CRI · 24 hours
- Emergent situations / Colloid oncotic pressure support · 10/mL/kg/day · IV · slow bolus over 15-30 minutes OR 24-hour infusion
- Shock resuscitation · 20 mL/kg · IV · bolus · Slower in the cat. Rapid administration to cats can cause nausea and vomiting.
- Adult horses - volume support · 8-10 mL/kg/day · IV · daily
- Foals - rapid volume support · 3-5 mL/kg · IV · once · In addition to crystalloids.
- Hypo-oncotic, well hydrated horses · 0.5-1 mL/kg per hour, up to 10 mL/kg/day · IV · CRI
- Volume replacement · 3-10 mL/kg · IV · once · Total daily doses of 10 mL/kg should not be exceeded due to risk for coagulopathies.
- Fluid resuscitation and management of hypoproteinemia · 8-10 mL/kg IV bolus or as a CRI at 0.5-1 mL/kg/hr (max. of 10 mL/kg/day) · IV · bolus or CRI
- Volume replacement · 10-15 mL/kg over 20-40 minutes, up to four times daily, OR 10-15 mL/kg bolus over 20-40 minutes followed by 1-2 mL/kg/hr continuous rate infusion · IV · up to q6h or CRI · Recommended maximum dose is 20 mL/kg/24 hours, though author notes exceeding this without side effects.
給藥途徑
禁忌症
- Severe heart failure
- Severe bleeding disorders
- Oliguric or anuric renal failure
不良反應
- Coagulopathies (prolonged PT/PTT, altered Factor VIII and von Willebrand Factor)
- Nausea and vomiting (especially in cats if administered too rapidly)
- Volume overload leading to pulmonary edema
- Hypersensitivity/anaphylactic reactions (rare)
- Falsely elevated serum amylase levels
- Transient increases in indirect serum bilirubin
- Potential risk for acute kidney injury (extrapolated from human data)
藥物相互作用
- Whole Blood / Red Blood Cells · Do not administer Hextend simultaneously with blood through the same administration set due to a risk of coagulation.
監測
- Fluid status (blood pressure, heart rate, capillary refill time, central venous pressure)
- Coagulation parameters (PT, PTT, platelet count), especially in high-risk patients or with high doses
- Clinical signs of pulmonary edema (respiratory rate/effort, lung auscultation)
- Blood gases
- Renal function (BUN, creatinine, urine output)
過量
Overdosage primarily results in **intravascular volume overload**, which can lead to pulmonary edema and congestive heart failure in susceptible patients. Treatment involves stopping the infusion, carefully monitoring fluid status, and administering diuretics (e.g., furosemide) if pulmonary edema develops.
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